Standardization of the LTE (Long Term Evolution) system (Rel. 8 and Rel. 9), which is a radio communication system for 3.9th generation mobile phones, has been completed, and the LTE-A (LTE-Advanced, also referred to as IMT-A, for example) system (Rel. 10 and thereafter) as a more advanced LTE system is currently being standardized as one of the 4th generation radio communication systems.
In the LTE system and the LTE-A system, it is necessary to cope with a rapid increase in data traffic, and securing frequency resources is one of the significant issues in addition to introducing a technique of increasing a peak data rate and frequency use efficiency. In the LTE system and the LTE-A system, it has been assumed so far to use a frequency band which is referred to as a so-called licensed band whose license is obtained from a country or an area where a cellular operator provides a service, and an available frequency band is limited.
Thus, it has been discussed recently to provide the LTE system (also referred to as LTE-U) using a frequency band which is referred to as a so-called unlicensed band that does not require a license from a country or an area (refer to NPL 1). In the LTE-A system, a CA (Carrier Aggregation) technique has been adopted in which one system band of the LTE system is set as a component carrier (CC, also referred to as a Serving Cell) and a plurality of CCs are used to perform communication. It is expected to apply the CA technique also to the unlicensed band and utilize the unlicensed band by LAA (Licensed Assisted Access) using information provided from the licensed band, as one of the methods with which a rapid increase in data traffic is able to be coped with.
In addition, not only the unlicensed band but also a frequency band called a white band (white space) which is not actually used but is provided for preventing interference between frequencies (for example, a frequency band which has been allocated for television broadcasting, but is not used in some areas) and, a shared frequency band which has been exclusively allocated to a specific operator so far, but is expected to be shared between a plurality of operators in the future, and other bands are also considered to be used for cellular communication in the future.
Meanwhile, in the LTE system and the LTE-A system, when a terminal apparatus (a terminal, a mobile terminal, a mobile station, UE; User Equipment) receives signals of a plurality of base station apparatuses, a base station apparatus to be connected is decided by using a measurement result of receive power or the like. First, the terminal apparatus detects PSS/SSS (Primary Synchronization Signal/Secondary Synchronization Signal) which are synchronization signals and identifies a cell ID. Then, the terminal apparatus receives a reference signal of a sequence generated with use of a cell ID, in a resource which is decided in accordance with the cell ID and in which the reference signal is transmitted, and measures receive power. By reporting the receive power of the signals from the plurality of base station apparatuses to the base station apparatus which has been connected, the terminal apparatus receives an instruction of handover from the base station apparatus or transmits a scheduling request in a case of initial connection, thereby being able to be connected to the base station apparatus from which the terminal apparatus is able to obtain high receive power.